1. Field of the Invention
This invention pertains to the field of electrical communications, more particularly the field of continuous variable indication or telemetering, and to the field of electrical computers and data processing systems, more particularly the field of measuring, testing, or monitoring systems having programmed testing conditions.
2. Description of the Prior Art
In a typical telemetry station, digital data representing periodically sampled measurements of a number of variables is received serially from a relatively small number of carrier frequencies in successive frames each having a synchronization word followed by a predetermined number of data words corresponding to individual variables. Each frame is decommutated into successive parallel data words each representing one sample of a variable. The parallel words are directed by a demultiplexer to analog conversion providing an analog output for each variable. The output is directed to a pen of a recorder. Different tests providing telemetered data have different frame formats and use the same pen for different variables having different ranges and transmitted by a different modulation type and/or different digital arithmetic format.
As a result, a telemetry system must be reconfigured, at least partially, for each test. In prior art telemetry systems, patch panels and the like are used to direct digital and analog data and to select limited arithmetic format conversions. The necessary patch panel rewiring between tests is time consuming and error prone. Since the configuration for every test is different, it is not practical to maintain completely wired panels and extensive rewiring is frequently required even for similar but not consecutive tests. Programmable digital devices have been developed for data flow direction and conversion in telemetry systems, but such existing such devices provide limted data conversion, are not adapted for use with data arriving at high speed, or have volatile memories requiring reprogramming for every test.
The limited data range and format conversions available in existing telemetry systems frequently require recalibration of individual recorder pens to provide a desirable range of pen movement for different variables. This recalibration is another time consuming process which must be redone for each test.
The prior art includes data compressors for use with telemetry systems in which rapidly arriving data is stored for later analysis by a relatively powerful digital computer. Such a compressor receives successive decommutated parallel data words and is programmable to associate each data word with a tag word identifying the corresponding variable. The compressor provides a parallel output of corresponding tag and data words together with a strobe signal substantially as the data words are received by the compressor. Such a compressor is adapted for data compression by ignoring consecutive unchanged values of the same variable, but also provides a "throughput mode" in which every data word is output with its tag word. Typically, the programming of existing data compressors for tag and data association is involved and data format and range conversion is not provided.